Influence of dynamic effects, sample thickness and absorption on a fine structure in an electron microscope pole figure

Abstract

A fine structure has been observed in electron microscope images of ⟨111⟩ pole figures of cubic dysprosium sesquioxide. The observed lines are shown to be due to upper-Laue-zone reflections, but the measured voltage values for which they cross at the centre of the figure pole do not correspond to a situation in which the involved reflections are on the Ewald sphere. This shift between the measured crossing-voltage value and the kinematic value can arise for several reasons.

Calculations have been made to ascertain the respective influences of dynamic interactions, absorption or crystal thickness on this shift. We show that, for our specimens, the influence of thickness or absorption is rather weak. The shift in crossing values is mainly due to interactions between diffracted beams, not only from the zero-order zone but also from the upper Laue zone.